Method of and machine for finishing gear teeth



p J. M. CHRISTMAN 2,328,783

METHOD OF AND MACHINE FOR FINISHING GEAR TEETH Filed April 24, 1940 Patented Sept. 7, 1943 UNlTED-pLSTATES PATENT err-Ice Melanoma on eN-n'MAoHma FOR mNrsnrNG H GEAR TEETH John Christrhan, DetreiLlWieh assigner to Packard MeterLCzirCompany, Detroit, Mich, a v corporation ofMichigan Apml ica-fienilpril 24, 194i), tSerial Ne. 3531,4119

(C1. l9ll.1.6-)

7 Illalims.

This invention relates to a method of and-rappar-atus for finish i-ng'helical 'gears.

The teeth of helical gears generated by cutters to bear along their entire faces when drivingin meshed relation will be sprung by pressure so that only the end portions of the faces contact, and ash consequence noisy operation results. in erder to overcome this .eoncli'tien ill, ls-11.5- tom'ary to provide cutters that will generate a zone intermediate the ends of fthefaces of the gear teeth :so that there will h no eon-- tact at the ends ott-he gear teeth when operatin'ginmated relation underflead.

'Ihe generating eperatien generally leaues" the teeth of hypoid 'ring gears rough, and iinaecnrate as to pitch cone angle, teeth depth and radial angular "position. Ehandening "operation usually further distorts the teeth so that the finishing operation, iusual ly lapping the -mat ing gears, must remove considerable material Ito 'true up the gear teeth order to insure :qiiiet operation.

.It is an object of this invention to finish helical gears to CIOSG IimitS hetween the generating and hardening operations :by -as'having and hurn'i'shing process to. reduce the lappingoperation required.

Another object -ef the invention is provide an improved method for quickly and accurately finishing hypoid gears, after a teoth generating operation forming the faces of the teeth with hearing .zones intermediate their ends, in which the hearing :zone 'and the :adjacent end zones :ef the traces of the teeth are shaved and burmshed; substantially individually.

' .A .turther object .Gf lthe inwntion is to provide apparatus for shaving teeth to closeflismits. x e w Still another object f the invention is lto provide apparatus having v.azplurality of shaving and burnish-mg cutters :that .will operatezin different spiral gear zones iineally of the iteeth of a spiral gSErjiO- materially reduce the error that is present after a :teoth generating ieperation :torming the hear-' ing zones intermediate the .ends of the fanes -:of the teeth.

Still another object :ef the invention :resideszin apparatus ifor accurately ishaving *hurnishing spiralv gears by means of 'which'ran equalized pressureis jprovidedto produce a similar cutting. action on the teeth even though their-depth may vary. 7 l

=ther objects:oftheinvention will.appearfsrem the ifollmeing description :taken connection with the drawing, "which forms apart-oi this speeificamiongzmdiin which:

Fig. 1 is a perspective View of an apparatus employed as the driving element o'f'a anotorwehicle axle structure. The teeth =l l of such hype'id gear are usually first=generatedhy a suitable cutter and then hardened, a'fter which-error in the teeth, resulting from in-accuracies ofthe g'enerating operation and distortion resulting tre'm the hardening process, is removed to some extent by a final lapping operation. The genereting op oration can be such that the-centralnone er the ;faces of the teeth form the demeanor bearmg areas when meshing with a mated pinion gear. Ordinarily the faces of the teeth are rough'after the tooth generating operation and the pitch cone angle, the teeth depth and radial angular position may varyto some extent. The'hajrdening operation tends to further increase thesdfiaccurate toeth conditions-so that considerable material must be removed during-the lapping operation. The' lapping operationis new and increases manufacturing cost unduly when these extensiveteeth corrections areencountered. ln order to reduce the extent ofthe lapping-oper-ation, this invention proposes to shave and burni-sh the gear teeth to close "limitsf between the tooth generating and hardening operatiensn Apparatus by 'meansof'which the invention ean be carried out consists generally of -a. heel i-2, cutter units A, B *and-C, pilot means i 4 oa-rrieii by the bed and Work gear pressure and drive means '15. The-.bedls'suitablyfiinedomen-suitable stationary support enet shown Y-and emsthree wings l-B ferminga mounting for thecutt'er A collar or flange l extendsupwartlly -trem the central portion of the bed and receives the r'otatable stem 5 8 of a -circul-arpilot hea'd l fl that corresponds in diameter to the central "opening throughthe hypoid'ring gear. z l

'The :cutter units each inclutlefia housing '20 carrying bearings 21 through which shatt n-ex tends. Thesehousingsbare adjustablyesecnred :on

the :bed wings by suitable fastening tmeans in the form of 3 bolts :23 that extend through elongated slots 2'4 in the housings. These slots allow ad justment of the housings on the bed in the direction of the axis of the shaft carried thereby and the slots are wide enough to allow the housings to be bodily adjusted laterally a limited extent. The vertical position of the housings can be varied by suitable shims 25 placed between the housings and the bed.

The cutters 26 for shaving and burnishing the work gear are fixed to the inner ends of the shafts and they are in the form of gears having spiral teeth 21. Any number of cutting units can be employed but three are preferably used so that the hypoid gear when placed thereon in mesh with the cutter teeth will have a floating three-point mounting. The spiral teeth of the cutters are formed on their faces with radially extending grooves 23 and similar grooves in the teeth are staggered relatively lineally of the teeth so that the cutting. edges formed thereby will not operate in the same .path, thus avoiding the creation of ribs on'the work gear teeth which :otherwise would be formed. V v 7 The arrangement .of the cutters is such that the shaving and burnishing portions of their teeth are effective upon different portions or zones of the work gear teeth in a lineal direction. This result can be accomplished either by the length of the cutters, or by formation of their teeth so that only alineal portion thereof will function to shave and burnish. The zones on the work gear teeth operated upon by the cutters can be separated, they can ,overlap, or they can adjoin at their ends. Inthe drawing, I have illustrated cutters that will shave and burnish the entire length of the work gear tooth surfaces with some overlapping of the zones operated upon lineally. With the illustrated arrangement, as shown best in Fig. 2, the cutter A operates, on the work gear tooth surfaces in thelineal zone A, the cutter B operates on the work gear tooth surfaces in the lineal zone B and the cutter C operates on the work gear tooth surfaces in the zone C. r I

H In this method of simultaneously shaving and burnishing gear teeth, the hypoid ring gear is positioned on and in intermeshing relationship with the cutters with the pilot head 59 extendingthrough the centralopening thereof. The cutters are properly adjusted so that they .Will operate in their zones as required to finish the hypoid ring gear. Due to the fact that the ring gear has a three-point supporton the cutters, it will float thereon and compensate for varying tooth conditions under vertical pressure when rotated so that the teeth will be finished uniformly;

The shaving and burnishing operation results from theapplication of the pressure and driving means to the work gear. A spindle 30 carryinga head 3| is arranged above the cutters and is suitably rotated and controlled forvertical movement. This head carries driving pins 32 projecting from itslower, face that are arranged to register with and enter openings 33 formed in the ring gear. After positioning the ring. gear in piloted intermeshing relationship with the cutters, the driving head 3! is lowered to drivingly couple with the ring gear, and there after the head is rotated while applying pressure thereagainst in an axial direction. Thus the ring gear is rotated while being .pressed against the contacting shaving and b-urnishing portions of theteethof the cutters that are in mesh withthe work: gear. Surplus metal will appended claims.

be removed from the three zones of the ring gear teeth so that the errors in each zone will be accurately corrected individually, except of course where the zones overlap. Thus each zone of the gear teeth can be substantially individually corrected.

, With themethod and apparatusherein described, helical gears can be quickly; and more accurately finished than previously.

Although the invention has been described in connection with a specific embodiment, th prin ciples involved are susceptible of numerous other applications which will readily occur to persons skilled in the art. The invention is therefore to be limited only as indicated by the scope of the What is claimed is:

' 1. The method of simultaneously shaving and burnishing helical gears which comprises positioning such a gear in an intermeshing relationpressure thereagainst in the direction-of th 'cut;-

ters. I

.2. The method of simultaneously :shaving. and burnishing'a hypoid ring gear which comprises positioning such a gear in intermeshingrelationship with rotatable cutters of helical geariorm arranged in equally spaced relationship circularly and so that the cutting portion of the teeth of each are in different stations radially of :thejhy-, poid gear teeth, and rotatingthe hypoidgear while pressing it against the cutters. 1

3. The method of simultaneously shaving and burnishing a hypoid ring gear which comprises positioningsuch a gear in piloted intermeshing relationship on rotatably mounted shaving and burnishing cutters, of helical gear form' with the cutting portionsof the teeth'of each cutter lying substantially in different zones lineally. of the hypoid gear teeth, and rotating the hypoid gear while pressing it againstthe cutters. 5 ".1:

4. A machine for finishing the teeth of a hypoid ring gear comprising a base,-a pilotonth base for centering thering gear, three'equall spaced shaving and burnishinggear'members on which the ring gear rests and meshes with, said mem-. bers being formedto shave and burnish'difierent zones lineally of the gear teeth; bearing faces, means on said base rotatably supporting said gear members, and-meansforrotating said rin and applying pressure therea'gainst. I T V 5. A machine. for finishing theteeth of 'a hypoid ring gear' comprising aibase, a pilot onthe base adapted to be telescoped by the ring'g'ear', "gear members on which the ringzgear: Jean frest' and mesh with, the teeth ofsaid gear'mernb'ersf being formed to shave. and burnish different zonesline ally of the faces of the ring gear teeth; means rotatably supporting 'the gear members on the base, said means being adjustable to shift'said gear members in either an axial or radialdi rec-r tion, and a spindle for rotating said ring .gear and pressing the same against the gear membersff 6. A machine for finishing the teethof' ahyp'oid ring gear comprising t'hree rotatably supported: equally spaced gear members; supporting means for the gear members adjustable toshift the posi-" tions of the gear members axially or radially',-" means for centering the ring gearin meshing relation with the gear members; the gear members having. effective tooth portions .for shaving and burnishing the ring gear-rteethflocatedvrelativelyz gear mounted on the base, said members being equally spaced andadapted to mesh With and support said ring gear, and a spindle having driving lugs engageable with the ring gear for rotating and pressing the same against the members, said members being formed to shave and burnish different zones radially on the ring gear teeth.

' JOHN M. CHRISTMAN. 

